One Flew Over the Cuckoo's Nest is about a prisoner Randle Patrick Mac McMurphy who was serving prison time for statutory rape. He is then transferred to a mental institution. Mac uses this opportunity at the mental hospital to escape going back to prison. He hopes that he could serve the rest of his sentence in the mental hospital. The mental hospital is not the pleasant environment that Mac thought it would be.
The ward is ran by an unbending rule nurse Mildred Ratched. She pushes her patients to the limits with mental stress and unwanted medical treatments. The patients are afraid of Ratched and are more focused on her than their treatment plan. Mac immediately defines himself as a leader. He gathers a group of other patients Billy Bibbit, Charlie Cheswick, Martini, Dale Harding, Max Taber, Jim Sefelt, and Chief Bromden all who suffer from mental illnesses from paranoia, delusions, anxiety, and tempers amongst other illnesses.
Nurse Ratched and Mac are at a constant battle over leadership within the hospital. Mac wins a card game and wins cigarettes. Nurse Ratched is outrage and takes away the cigarettes and gives them out to the other patients. Mac is furious he wants a vote to change the policy within the hospital. Mac steals the hospital bus and takes his friends along with him. They pick up a girl who likes to party candy and goes deep sea fishing. This escape allows the patients to feel a sense of freedom and determination that anything is possible.
The group however returns to the hospital and Mac realizes that Ratched and the doctors can commit him in the hospital. Mac and Ratched's struggles are getting out of control and Mac wants to escape. He calls Candy and she brings a friend. They all break into the medicine cabinet and have a Christmas party with sex and booze. The next morning nurse Ratched discovers the mess and Mac chokes her near to death.
Chief sees a lobotomy scare on makes forehead and he decided to suffocate Mac instead of allowing him to live like that. Mac is finally free from the confinements of any institution.